#include <iostream>
#include <algorithm>
using namespace std;
int flag = 1;
int Binary_Search(int *a, int n, int key) {
    int low, high, mid;
    low = 0;
    high = n - 1;
    while(low <= high) {
        mid = low + (high - low) * (key - a[low]) / (a[high] - a[low]);
        if(key < a[mid]) high = mid - 1;
        else if(key > a[mid]) low = mid + 1;
        else return mid;
    }
    flag = 0;
    return flag;
}
int main() {
    int n, key;
    int *a = new int [100];
    cin >> n;
    for(int i = 0; i < n; i++)
        cin >> a[i];
    sort(a, a + n);
    cin >> key;
    int pos = Binary_Search(a, n, key);
    if(flag) cout << "The element position is " << pos << "." << endl;
    else cout << "The element is not exist." << endl;
    return 0;
}
